Chapter 124:13 & 14
Laws Of Tish'ah B'av
13. It is forbidden to greet someone on Tish'ah B'av (1). It is even
forbidden to exchange greetings like "good morning" and the like. If one
is greeted by a Gentile or by a Jew who is not familiar with the law ("am
ha'aretz"), one should reply in a soft tone, so as not to arouse ill
feeling (that might occur if one wouldn't reply at all) (2).
It is also forbidden to send a gift to a colleague [on Tish'ah B'av],
because that is included in the prohibition against greeting.
14. One should not go for pleasure walks through public places [on Tish'ah
B'av], lest it lead to frivolity ("s'chok") and joy ("simcha") (3).
There are authorities who prohibit smoking tobacco [on Tish'ah B'av];
others permit it after midday (4), in the privacy of one's own home (5).
FOOTNOTES:
(1) In Hebrew, the prohibition is phrased "lish'ol b'shlom chavero." The
same prohibition applies to one who is mourning the death of a close
relative (during the first seven days after the burial); on Tish'ah B'av we
are all considered mourners over the destruction of the Beit Hamikdash.
(2) Where appropriate, one should inform the Jew about the prohibition
against greeting on Tish'ah B'av, so as to avoid any feelings of resentment
(Mishna Berura 554:42).
(3) Engaging in any unnecessary activity that would divert one's mind from
mourning is prohibited (Ibid. 43). Therefore, one should not engage in idle
conversation (Ibid.659:41).
(4) That is, after halachic "chatzos."
(5) It should be noted that these authorities were writing long before it
was known that smoking is a potentially lethal addiction.